Gas Sensor for Sensing Gases in an Environment

This application claims priority to and the benefit of co-pending U.S. Provisional Application 63/671,736, filed on Jul. 15, 2024, entitled “MULTIPIXEL GAS SENSOR SYSTEM DESIGN”, by Goel et al., having Attorney Docket No.IVS-1135-PR, and assigned to the assignee of the present application, which is incorporated herein by reference in its entirety.

Certain gas sensors rely on physical changes or chemical changes in a chemical sensing material while in the presence of a gas to determine concentration of the gas in a surrounding environment. Current gas sensors, such as those typically used in consumer or automotive applications, are only capable of identifying a single gas, requiring separate gas sensors for each gas to be sensed.

The following Description of Embodiments is merely provided by way of example and not of limitation. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding background or in the following Description of Embodiments.

Reference will now be made in detail to various embodiments of the subject matter, examples of which are illustrated in the accompanying drawings. While various embodiments are discussed herein, it will be understood that they are not intended to limit to these embodiments. On the contrary, the presented embodiments are intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope the various embodiments as defined by the appended claims. Furthermore, in this Description of Embodiments, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present subject matter. However, embodiments may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the described embodiments.

Discussion includes a description of example gas sensors for sensing gases in an environment, in accordance with various embodiments. Discussion begins with a description of example gas sensors including a plurality of sensing elements. Discussion continues with a description of an example sensing element including a gas sensitive material. Discussion continues with a method for sensing gases in an environment using a gas sensor of the described embodiments.

Embodiments of a gas sensor including a plurality of sensing elements are described herein. The sensing elements include a gas sensitive material and a plurality of electrodes. In some embodiments, the sensing elements also include a heater and a temperature sensor, and are configured for individual temperature control. In some embodiments, during operation, the sensing elements each have at least one different parameter, including both physical parameters (e.g., material composition of the gas sensitive material or electrodes, physical dimensions of the gas sensitive material, etc.) and operational parameters (e.g., temperature, temperature cycling, probing frequency, etc.)

The embodiments described herein provide a gas sensor that can utilize multiple and/or different types of gas sensitive materials to perform gas sensing in an environment. The sensing methodology using the described gas sensor uses one or more measured electrical properties of the gas sensitive materials, such as resistance, capacitance, and other non-linear electrical behavior at single or multiple probing frequencies. In some embodiments, the gas sensor is also configured to individually control a temperature of the sensing elements. It should be appreciated that the temperature of the sensing elements can be controlled to be a static temperature or a dynamic temperature that changes over time. Moreover, the rate and frequency of temperature change of the sensing elements can be controlled as well. The gas sensor utilizes control circuitry that drives the sensing elements of the gas sensor and processes the data received to identify a gas type. In some embodiments, a gas concentration can also be identified. In some embodiments, the gas sensor is an embedded microelectromechanical systems (MEMS) application-specific integrated circuit (ASIC). In some embodiments, the control circuitry is embedded within the MEMS ASIC.

The described embodiments provide a gas sensor and method of using a gas sensor where the gas sensing properties of the gas sensor can be tuned by operational parameters (such as operational temperature control, temperature cycling, probing frequency and waveform, material thickness, etc.), and physical parameters, such as a choice of gas sensitive materials and/or dimensions, choice of electrode materials, etc. The gas sensor can also provide multiple outputs from a single gas sensitive material. The gas determination can process from the gas sensor, as well as an optional ambient environmental sensor (e.g., relative humidity, temperature, or pressure), and determines gas types and concentrations.

Embodiments described herein provide a gas sensor for sensing gases in an environment, where the gas sensor includes a substrate, a plurality of sensing elements, control circuitry, and a gas determination module. In some embodiments, the substrate and the plurality of sensing elements are included within a microelectromechanical systems (MEMS) device. In some embodiments, at least one of the control circuitry and the gas determination module is embedded within the substrate. In other embodiments, the control circuitry and the gas determination module are included within a separate device.

A sensing element of the plurality of sensing elements includes a structure coupled to the substrate, a gas sensitive material overlying the structure, and a plurality of electrodes underlying the gas sensitive material. In some embodiments, the structure includes a suspended bridge structure. In some embodiments, the structure includes a diaphragm. In some embodiments, the structure includes a portion of the substrate. In some embodiments, each sensing element of the plurality of sensing elements includes the same gas sensitive materials. In other embodiments, each sensing element of the plurality of sensing elements includes different gas sensitive materials. In some embodiments, electrodes of at least one sensing element include a different material composition than electrodes of other sensing elements of the gas sensor. In some embodiments, the sensing elements further include a heater and a temperature sensor. In some embodiments, the sensing elements further include a heat spreader for distributing heat evenly across the sensing elements.

In some embodiments, the gas sensor includes an environmental sensor, where the environmental sensor includes at least one of a temperature sensor, a pressure sensor, and a relative humidity sensor. In other embodiments, the gas sensor receives measurements from an external environmental sensor as an input.

The control circuitry is for measuring electrical properties of the gas sensitive materials of the plurality of sensing elements. In some embodiments, the control circuitry is configured to control a temperature of the plurality of sensing elements. In some embodiments, the control circuitry is configured to drive at least two sensing elements of the plurality of sensing elements to different temperatures. It should be appreciated that the temperature of the sensing elements can be controlled to be a static temperature or a dynamic temperature that changes over time. Moreover, the rate and frequency of temperature change of the sensing elements can be controlled as well. For example, a temperature of a sensing element can be set to change or cycle between two or more temperatures at various time intervals, allowing for the measurement of electrical properties that are indicative of how gas sensitive material transitions over time.

In some embodiments, the electrical properties measured by the control circuitry includes a resistance of the gas sensitive material. In some embodiments, the electrical properties measured by the control circuitry includes a capacitance of the gas sensitive material. In some embodiments, the electrical properties measured by the control circuitry includes a combination of resistance and capacitance of the gas sensitive material. In some embodiments, the electrical properties are measured by the control circuitry at a plurality of sensing element temperatures. In some embodiments, the measurement of the electrical properties of the gas sensitive material taken at a plurality of temperature is indicative of the time rate of change of the electrical properties. In some embodiments, the electrical properties measured by the control circuitry are at a plurality of probing frequencies.

The gas determination module is configured to identify at least one gas in the environment based at least in part on the measured electrical properties. In other embodiments, the gas determination module is further configured to identify at least one gas in the environment based at least in part on a measurement of an external environmental sensor. In some embodiments, the gas determination module is further configured to identify at least one gas in the environment based at least in part on a measurement of the environmental sensor.

In accordance with some embodiments, a gas sensor device including multiple sensing elements is described. The gas sensor device is configured to identify at least one gas in an environment based at least in part on measuring the electrical properties of gas sensitive materials of the multiple sensing elements.

1 FIG.A 2 FIG. 100 100 102 104 100 110 110 110 130 130 130 110 230 232 110 110 100 140 150 102 100 110 110 a n a n a n is a diagram illustrating a cross-section views of example gas sensor devicefor sensing gases in an environment, according to some embodiments. Gas sensor deviceincludes a substrateincluding a cavity. As illustrated, gas sensor deviceincludes multiple sensing elements(illustrated as sensing elements-) comprising one or more gas sensitive materials(illustrated as gas sensitive materials-). Each sensing elementalso includes at least two electrodes (e.g., electrodesandof). It should be appreciated that the electrodes of each sensing element-can have the same material composition, a different material composition, or any combination thereof. Gas sensor devicealso includes control circuitryand gas determination module, where are embedded within substrate. It should be appreciated that gas sensor devicecan include any number of sensing elements, so long as there are at least two sensing elements.

102 100 102 104 120 120 110 110 102 120 120 102 120 120 102 104 110 110 120 120 120 102 a n a n a n a n a n In some embodiments, substrateof gas sensor deviceis a CMOS substrate layer, where substrateincludes cavity. Structuresthrough, each of which corresponds to a sensing elementsthrough, are deposited or formed on substrate. For example, structures-can be etched to substratevia wet etching or dry etching. Furthermore, the etching of structures-to substratecan be an isotropic etch or an anisotropic etch (e.g., a deep reactive ion etching, etc.). Cavitycan thermally isolate sensing elements-. In some embodiments, structureincludes a suspended bridge structure. In some embodiments, structureincludes a diaphragm. In some embodiments, structureincludes a portion of substrate.

120 120 130 130 100 130 120 130 130 110 130 a n a n a n Structure-can provide mechanical support for gas sensitive materials-of gas sensor device. Gas sensitive materialscan be deposited, formed, printed, or otherwise placed on structures. The material type, composition, and physical properties (e.g., thickness, particle size, etc.) of gas sensitive materials-can be controlled during fabrication. It should be appreciated that each sensing elementcan include the same, different, or any combination of gas sensitive materials, as well as the same, different, or any combination of material type, composition, or physical properties.

130 130 130 130 a n a n Gas sensitive materials-can include a metal oxide, such as but not limited to, an oxide of chromium, manganese, nickel, copper, tin, indium, tungsten, titanium, vanadium, iron, germanium, niobium, molybdenum, tantalum, lanthanum, cerium or neodymium. In other embodiments, the gas sensitive materials-can be composite oxides including binary, ternary, quaternary and complex metal oxides.

2 FIG. 110 100 110 120 230 232 130 230 232 120 230 232 130 230 232 230 232 230 232 230 232 140 100 is a diagram illustrating an example sensing elementof gas sensor device, according to some embodiments. Sensing elementincludes structure, electrodesand, and gas sensitive materialoverlying electrodesandand structure. Electrodesandcan be employed to detect changes in the gas sensitive material. For example, electrodesandcan be employed to detect changes in the electrical properties of the chemical sensing material as a concentration of a target gas changes. Electrodesandcan be made of a conductive material, such as a noble metal. For example, the electrodesandcan comprise titanium nitride, polysilicon, tungsten, gold, platinum, another metal, etc. In one example, electrodesandcan be electrically coupled to another component (e.g., control circuitry) of gas sensor device.

110 240 242 110 244 In some embodiments, sensing elementincludes heaterand temperature sensor. In some embodiments, sensing elementalso includes heat spreaderfor distributing heat evenly across the sensing elements.

140 230 232 110 110 110 110 140 110 110 240 242 110 110 140 110 110 110 110 110 110 110 110 110 110 110 110 130 1 FIG.A 2 FIG. a n a n a n a n a n a n a n a n a n a n Control circuitryofis electrically coupled to the electrodes (e.g., electrodesandof) of sensing elements-, and is configured to control operation of sensing elements-. Control circuitrycontrols the temperature or temperatures of sensing elements-by utilizing heaterand temperature sensorof each sensing element-. It should be appreciated that control circuitryis configured to control the temperature of each sensing element-independently, and control each sensing element-to a desired temperature, such that each sensing element-can be driven to the same temperature, different temperature, or any combination thereof. It should be appreciated that the temperature of sensing elements-can be controlled to be a static temperature or a dynamic temperature that changes over time. Moreover, the rate and frequency of temperature change of sensing elements-can be controlled as well. For example, a temperature of a sensing element-can be set to change or cycle between two or more temperatures at various time intervals, allowing for the measurement of electrical properties that are indicative of how gas sensitive materialtransitions over time.

140 130 130 110 110 140 140 130 130 110 110 a n a n a n a n. Control circuitryis also configured to measure electrical properties of gas sensitive materials-of sensing elements-. Examples of the electrical properties that are measured by control circuitryinclude, without limitation: resistance, capacitance, a combination of resistance and capacitance, and non-linear electrical element values. The electrical properties can be measured at one or more probing frequencies. The electrical properties can be measured at one or more temperatures at different times or frequencies. Control circuitryis also configured to measure response dynamics of the gas sensitive materials-of sensing elements-

100 160 160 160 102 160 140 160 1 FIG.A 1 FIG.B In some embodiments, gas sensor devicealso includes at least one environmental sensor(e.g., an ambient environmental sensor). The environmental sensorcan include at least one of a relative humidity sensor, a temperature sensor, or a pressure sensor. As illustrated in, environmental sensoris embedded within substrate. However, it should be appreciated that environmental sensorcan also be an external sensor, such that control circuitryreceives input from an external environmental sensor(e.g., as shown in).

150 140 150 160 150 160 Gas determination moduleis communicatively coupled with control circuitry, and is configured to identify at least one gas in the environment based at least in part on the measured electrical properties. In some embodiments, gas determination moduleis further configured to identify the at least one gas in the environment based at least in part on a measurement of environmental sensor. In other embodiments, gas determination moduleis further configured to identify the at least one gas in the environment based at least in part on a measurement of an external environmental sensor.

150 130 130 100 150 150 150 a n In some embodiments, gas determination moduleimplements a methodology for processing the measured electrical properties of the gas sensitive materials-to determine at least one gas present in the environment in which gas sensor deviceresides, as well as the respective concentrations of the gas(es) present. In some embodiments, gas determination moduleincludes a trained AI machine learning model that is configured to determine the gases and concentrations in an environment based on the measured electrical properties. In some embodiments, gas determination moduleincludes an analytical model that is configured to determine the gases and concentrations in an environment based on the measured electrical properties. In some embodiments, gas determination moduleis configured to perform principal component analysis to determine the gases and concentrations in an environment based on the measured electrical properties.

1 FIG.B 1 FIG.A 180 180 100 140 150 160 102 140 150 190 110 110 192 160 140 150 194 a n is a diagram illustrating a cross-section views of example gas sensor devicefor sensing gases in an environment, according to other embodiments. Gas sensor deviceoperates in a substantially similar manner as gas sensor deviceof, with the exception of control circuitry, gas determination module, and environmental sensorbeing external to substrate. As illustrated, control circuitryand gas determination moduleare comprised within substrate, and are communicatively coupled to sensing elements-via electrical connector. Environmental sensoris communicatively coupled to control circuitryand gas determination modulevia electrical connector.

3 FIG. 100 100 102 110 110 110 104 110 130 130 130 230 232 230 230 232 232 a n a n a n a n is a diagram illustrating a top view of an example gas sensor devicefor sensing gases in an environment, according to some embodiments. As illustrated, gas sensor deviceincludes substrateand multiple sensing elements(illustrated as sensing elements-) overlying cavity. Each sensing elementincludes one or more gas sensitive materials(illustrated as gas sensitive materials-) and electrodesand(illustrated as electrodes-and-, respectively).

4 FIG. 1 3 FIGS.A through 410 420 430 410 420 430 110 As described above, the material type, composition, and physical properties (e.g., thickness, particle size, etc.) of gas sensitive materials can be controlled during fabrication. Different material types, compositions, and physical properties provide for the tuned measurement of the electrical properties of the gas sensitive materials.is a diagram illustrating example sensing elements,, and, of a gas sensor device having gas sensitive materials of different thicknesses, according to some embodiments. It should be understood that sensing elements,, andare examples of sensing elementof, and/or shown to illustrate relative thicknesses of gas sensitive materials on sensing elements of the same gas sensor device.

4 FIG. 410 414 412 420 414 412 430 414 412 414 414 a a b b c c a c As illustrated in, sensing elementincludes gas sensitive materialoverlying structure, sensing elementincludes gas sensitive materialoverlying structure, and sensing elementincludes gas sensitive materialoverlying structure, where gas sensitive materialsthrougheach have different thicknesses. Using gas sensitive materials of different thicknesses, as in the illustrated embodiment, provides for controlling the measurement of the associated electrical properties for each sensing element.

5 FIG. 1 1 3 FIGS.A,B, and 140 illustrates an example process of sensing gases in an environment, according to some embodiments. Procedures of these methods will be described with reference to elements and/or components of various figures described herein. It is appreciated that in some embodiments, the procedures may be performed in a different order than described, that some of the described procedures may not be performed, and/or that one or more additional procedures to those described may be performed. The flow diagrams include some procedures that, in various embodiments, are carried out by control circuitry (e.g., control circuitryof). In some embodiments, the control circuitry is controlled by one or more processors (e.g., a host processor or a sensor processor) under the control of computer-readable and computer-executable instructions that are stored on non-transitory computer-readable storage media. It is further appreciated that one or more procedures described in the flow diagrams may be implemented in hardware, or a combination of hardware with firmware and/or software.

5 FIG. 1 FIG.A 3 FIG. 500 500 With reference to, flow diagramillustrates an example process of sensing gases in an environment, according to some embodiments. In accordance with the described embodiments, flow diagramis performed using a gas sensor device including a plurality of sensing elements. A sensing element of the plurality of sensing elements includes a structure coupled to a substrate, a gas sensitive material overlying the structure, and a plurality of electrodes underlying the gas sensitive material. Examples of such gas sensor devices are described above in accordance withthrough

510 In some embodiments, as shown at procedure, a temperature of each sensing element of the plurality of sensing elements is controlled, wherein at least two sensing elements of the plurality of sensing elements are driven to different temperatures. It should be appreciated that the temperature of each of the plurality of sensing elements can be controlled to be a static temperature or a dynamic temperature that changes over time. Moreover, the rate and frequency of temperature change of the sensing elements can be controlled as well.

520 500 522 At procedureof flow diagram, electrical properties of a plurality of gas sensitive materials of a gas sensor device comprising a plurality of sensing elements are measured. In some embodiments, as shown at procedure, the electrical properties of the plurality of gas sensitive materials are measured at a plurality of probing frequencies. The electrical properties can be measured at one or more temperatures at different times or frequencies. In various embodiments, the electrical properties measured comprises at least one of: a resistance of the gas sensitive material, a capacitance of the gas sensitive material, and a combination of resistance and capacitance of the gas sensitive material.

530 At procedure, in accordance with some embodiments, environmental measurements from at least one environmental sensor are received. It should be appreciated that the at least one environmental sensor can be embedded within the gas sensor device or an external sensor that is communicatively coupled to the gas sensor device.

540 542 At procedure, at least one gas in the environment is identified based at least in part on the measured electrical properties. In some embodiments, as shown at procedure, the at least one gas in the environment is identified also based at least in part on the environmental measurements from the at least one environmental sensor.

What has been described above includes examples of the subject disclosure. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the subject matter, but it is to be appreciated that many further combinations and permutations of the subject disclosure are possible. Accordingly, the claimed subject matter is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.

In particular and in regard to the various functions performed by the above described components, devices, circuits, systems and the like, the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., a functional equivalent), even though not structurally equivalent to the disclosed structure, which performs the function in the herein illustrated examples of the claimed subject matter.

The aforementioned systems and components have been described with respect to interaction between several components. It can be appreciated that such systems and components can include those components or specified sub-components, some of the specified components or sub-components, and/or additional components, and according to various permutations and combinations of the foregoing. Sub-components can also be implemented as components communicatively coupled to other components rather than included within parent components (hierarchical). Additionally, it should be noted that one or more components may be combined into a single component providing aggregate functionality or divided into several separate sub-components. Any components described herein may also interact with one or more other components not specifically described herein.

In addition, while a particular feature of the subject innovation may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or a particular application. Furthermore, to the extent that the terms “includes,” “including,” “has,” “contains,” variants thereof, and other similar words are used in either the detailed description or the claims, these terms are intended to be inclusive in a manner similar to the term “comprising” as an open transition word without precluding any additional or other elements.

Thus, the embodiments and examples set forth herein were presented in order to best explain various selected embodiments of the present invention and its particular application and to thereby enable those skilled in the art to make and use embodiments of the invention. However, those skilled in the art will recognize that the foregoing description and examples have been presented for the purposes of illustration and example only. The description as set forth is not intended to be exhaustive or to limit the embodiments of the invention to the precise form disclosed.